(a) Field of the Invention
The present invention relates to a sensorless control method and system for a motor, and more particularly, to a sensorless control method and system for a motor that may more stably perform sensorless control in an ultra-high-speed driving region of a motor by adding a control model that considers iron loss of the motor to a back electromotive force (back EMF) observer and obtaining a more accurate electrical angle error that considers the iron loss through the control model.
(b) Description of the Related Art
As is well known to a person of ordinary skill in the art, a motor applied to an electrical turbocharger is a substantially small motor and thus it may be influenced by characteristic loss thereof. Generally, a permanent magnet motor may be operated without considering iron loss thereof. However, since such iron loss increases in proportion to speed of a motor, it is necessary to consider iron loss thereof when the motor is operated in an ultra-high-speed driving region (e.g., when a vehicle is travel at speed greater than a predetermined speed). Accordingly, it is required to operate an ultra-high-speed motor based on a control model considering iron loss.
Meanwhile, though it is required to accurately detect a position of a rotor of a motor while operating the motor, a sensor which may be configured to detect the position of the rotor in an ultra-high-speed region of the motor are not commercially available sensors. Accordingly, a sensorless control which does not use a sensor configured to detect the position of the rotor is required to operate the motor based on a control model therefor in a high-speed region thereof. However, since a sensorless control method for a motor according to the related art uses a control model that does not consider iron loss of the motor, an estimated electrical angle may become more inaccurate as speed of the motor increases causing a potential uncontrollable situation.
Referring to FIG. 1 illustrating a controller for a typical permanent magnet electric motor, a sensorless control method for the typical permanent magnet electric motor based on the back EMF observes the back EMF using an estimated d-axis and q-axis voltage commands and measured currents to obtain an electrical angle error. A phase-locked loop (PLL) controller is used to reduce the obtained electrical angle error. Estimated speed and electrical angle information may be obtained from output of the phase-locked loop controller, and may be used in a vector control of the motor.
To obtain the accurate electrical angle error, it is necessary to observe the back EMF, and the observation of the back EMF may be obtained from a motor control model. Generally, a motor control model not considering iron loss has been used, which may not be suitable for controlling an ultra-high-speed motor at which substantial iron loss occurs. Thus, the sensorless control not considering iron loss may cause a substantial electrical angle error in operating the ultra-high-speed motor.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.